This invention relates generally to a new process for converting round logs into lumber products, primarily dimension lumber. More particularly, it relates to a log cutting and subsequent rejoining process for converting logs to lumber products whereby the yield of lumber from the wood volume is substantially increased. In the commonly assigned U.S. Pat. Nos. 3,903,943 and 3,961,654 two cutting and rejoining processes are disclosed that can be utilized for increasing the lumber yield of logs which include certain of the steps employed in the cutting and rejoining process of the present invention. The disclosures in the above-noted issued U.S. Pats. are incorporated herein by reference for purposes of providing a complete description of the present invention.
The centuries-old conversion process of sawing logs into rectangular lumber results in a low yield in that, of the total volume of wood in a log, usually less than half is or can be converted into usable lumber. This is primarily because of the constraint that only square or rectangular pieces are cut from a cylindrical log. The actual lumber yields utilizing known processes, of course, vary depending upon a number of factors, such as log diameter, but even with the best available computer-controlled sawing machines a normal yield of lumber from a log is 60%-70% of the total wood volume and with small diameter logs much less. The term "lumber" is intended to mean those wood products traditionally having the highest marketable value that are derivable on a longitudinal sawing basis from a log and which are generally rectangular in cross-section.
The most commonly used large log-to-lumber converting process is that where saws make a plurality of longitudinal cuts through the log with each successive cut generally being in a plane parallel or perpendicular to the previous cut. With this process, it is obvious that there are yield limitations simply from the fact that the beginning raw material is cylindrical while the desired final lumber product is rectangular in nature. The wood volume not converted into lumber is utilized in a variety of other ways, none of which offer the value of a lumber product. The sawdust can be used as fuel, particleboard and the like. The solid wood slabs and edgings can be chipped into small pieces suitable for wood pulp production or likewise they can be used for fuel.
In the past, there have been many suggestions of ways to increase the recovery of solid wood products that could be converted from a log. Veneer production and subsequent laminating methods has been one suggestion. In veneer production the cylindrical log is converted into pieces of wood veneer which can then be laminated together to form various wood products. Such composite products and their converting processes do convert more of the wood volume into generally solid wood products, but they do not generally have the market acceptance or characteristics of lumber.
The aforementioned U.S. Pat. No. 3,961,654 discloses a process and resulting product that can be employed to greatly increase the yield of lumber from cylindrically-shaped logs. The process as disclosed is generally for logs of small diameter such as from 5 to 15 inches in diameter. It became apparent when considering larger diameter logs that cutting sector-shaped pieces according to the small log process would present difficult handling problems. For example, when cutting the larger diameter logs into sectors where the final lumber product was to have a nominal thickness of 11/2 inch, the sector angle would be relatively small and a large number of thin sectors would result which would be difficult to handle according to the process. Thus, the process of U.S. Pat. No. 3,903,943 was conceived to handle larger logs.
Yet another alternative process was conceived as following from cutting logs into sector-shaped pieces. The cutting and rejoining process of the present invention results in composite pieces which can then be machined into final shapes or machined for edge bonding into wider widths. It is anticipated that the resulting composite pieces of lumber will have a high value and will be generally accepted in the marketplace.
The composite pieces of lumber produced by the present process will have a substantially vertical grain pattern over their wide dimension. Thus, the resulting lumber products will have all the benefits and characteristics associated with typical vertical grain lumber, such as improved drying characteristics, better stability, and the like.
Accordingly, from the foregoing, one object of the present invention is to provide a process that will convert generally cylindrical logs into composite lumber products in which the percentage of log volume that is converted to lumber products is substantially increased.
A further object is to provide a lumber cutting and rejoining process that produces substantially all vertically grained lumber.
These and other objects will become more apparent and better understood upon reading the following specification in conjunction with the attached drawing.